No ‘Plan B’ for oceans, ac­cord­ing to new study


Tech­nol­ogy to drain heat­trap­ping CO2 from the at­mos­phere may slow global warm­ing, but will not re­verse cli­mate dam­age to the ocean on any mean­ing­ful timescale, ac­cord­ing to re­search pub­lished Mon­day.

At the same time, a sec­ond study re­ported, even the most ag­gres­sive timetable for re­duc­ing green­house­gas emis­sions will need a big boost from largely untested car­bon re­moval schemes to cap warm­ing to 2 de­grees Cel­sius above pre-in­dus­trial lev­els.

Above that thresh­old, say sci­en­tists, the risk of cli­mate calamity rises sharply. Earth is cur­rently on a 4 de­grees Cel­sius tra­jec­tory.

Both stud­ies, com­ing months be­fore 195 na­tions meet in Paris in a bid to forge a cli­mate pact, con­clude that deep, swift cuts in car­bon diox­ide (CO2) emis­sions are cru­cial.

Plan­e­tary-scale tech­ni­cal fixes — some­times called geo-en­gi­neer­ing — have of­ten been in­voked as a fall­back so­lu­tion in the fight against cli­mate change.

But with CO2 emis­sions still ris- ing, along with the global ther­mo­stat, many sci­en­tists are start­ing to take a hard look at which ones might be fea­si­ble.

Re­search has shown that ex­tract­ing mas­sive quan­ti­ties of CO2 from the at­mos­phere, through in­ten­sive re­for­esta­tion pro­grams or car­bon­scrub­bing tech­nol­ogy, would in the­ory help cool the planet.

But up to now, lit­tle was known about the long-term po­ten­tial for these mea­sures for restor­ing oceans ren­dered overly acidic af­ter two cen­turies of ab­sorb­ing CO2.

In­creased acid­i­fi­ca­tion has al­ready rav­aged coral, and sev­eral kinds of mi­cro-or­gan­isms es­sen­tial to the ocean food chain, with im­pacts go­ing all the way up to hu­mans.

Sci­en­tists led by Sabine Mathe­sius of the GEO­MAR Helmholtz Cen­tre for Ocean Re­search in Kiel, Ger­many used com­puter mod­els to test dif­fer­ent car­bon-re­duc­tion sce­nar­ios, look­ing in each case at the im­pact on acid­ity, wa­ter tem­per­a­tures and oxy­gen lev­els.

If hu­man­ity waited a cen­tury be­fore suck­ing mas­sive amounts of CO2 out of the at­mos­phere, they con­cluded, it would still take centu- ries, maybe even a thou­sand years, be­fore the ocean would catch up.

In the mean­time, they re­searchers say, corals will have dis­ap­peared, many marine species will have gone ex­tinct and the ocean would be rife with dead spots.

“We show that in a busi­ness-asusual sce­nario, even mas­sive de­ploy­ment of CO2 re­moval schemes can­not re­verse the sub­stan­tial im­pacts on the marine en­vi­ron­ment — at least not within many cen­turies,” Mathe­sius said.

Even in a sce­nario in which large-scale car­bon re­moval be­gins in 2050 — as­sum­ing such tech­nol­ogy is avail­able — the ocean does not fare well.

“Im­me­di­ate and am­bi­tious ac­tion to re­duce CO2 emis­sions is the most re­li­able strat­egy for avoid­ing dan­ger­ous cli­mate change, ocean acid­i­fi­ca­tion, and large-scale threats to marine ecosys­tems,” the re­searchers con­clude.

Sci­en­tists com­ment­ing on the study said it should sound an alarm.

“The threat of ocean acid­i­fi­ca­tion alone jus­ti­fies dra­matic and rapid re­duc­tion of CO2 emis­sions,” said Nick Ri­ley, a re­search as­so­ciate at the Bri­tish Ge­o­log­i­cal Sur­vey (BGS).

The sec­ond study, led by Thomas Gasser of the In­sti­tut Pierre-Si­mon Laplace, near Paris, uses state-ofthe-art mod­els to mea­sure the trade­off be­tween re­duc­ing emis­sions and car­bon-re­mov­ing tech­nolo­gies.

They show that even if na­tions strike a deal in Paris ad­her­ing to the most ag­gres­sive CO2-slash­ing path­way out­lined by U.N. sci­en­tists, it may not be enough to keep Earth on a 2 de­grees Cel­sius tra­jec­tory.

“Our re­sults sug­gest that neg­a­tive emis­sions” — the use of car­bon re­mov­ing tech­nol­ogy — “are needed even in the case of very high mit­i­ga­tion rates.”

To have a chance of meet­ing the 2 de­grees Cel­sius tar­get, 0.5 to 3.0 gi­ga­tonnes of car­bon — up to a third of to­tal an­nual CO2 emis­sions to­day from in­dus­try — would need to be ex­tracted ev­ery year start­ing more-or-less im­me­di­ately, they cal­cu­late.

The study ex­poses “an ele­phant in the room,” says Ri­ley.

“The tar­get to keep warm­ing within the 2-de­gree Cel­sius rise is look­ing in­creas­ingly unattain­able.”

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